<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="../vue.js"></script>
</head>

<body>
  <div id="app">
    <button @click="isHot = !isHot">点击切换天气</button>
    <p>今天天气真{{isHot? "热" : "冷"}}啊</p>
    <img :src="src" alt="">

    <ul>
      <li v-for="item in obj">{{item}}</li>
    </ul>
    <button @click="obj.a = 888">点击改变对象</button>
    {{count}}
  </div>
  <script>
    Vue.config.productionTip = false;

    const vm = new Vue({
      el: "#app",
      data() {
        return {
          isHot: true,
          src: "",
          obj: {
            name: "大理",
            age: "丽江",
            sex: "布达拉宫",
            a: 666
          },
          count: ""
        }
      },
    })

    //监听isHot
    vm.$watch("isHot", (value) => {
      //写在外面this指向window
      console.log(this);
      //用vm
      vm.src = value ? "./re.webp" : "./leng.gif"
    }, { immediate: true, })

    //监听obj
    vm.$watch("obj", (value) => {
      console.log("obj改变了");
      vm.count = value.a
    }, { deep: true })

  </script>
</body>

</html>